The use of ultrasonic equipment for detecting flaws in metal parts, as well as certain non-metallic parts, such as composites, is known in the prior art. When pulsed ultrasonic sound waves generated by a transducer or other mechanism are transmitted into a part to be inspected, internal defects or flaws, as for example, a crack, voids or other discontinuities in the part, will cause a portion of the sound wave impinging on the defect to be reflected back toward the transducer or other receiving mechanism. The time interval between the transmission of the sound pulse into the material being inspected and when the pulse reflected from the defect reaches the transducer is a measure of the distance between the point where the ultrasonic wave enters or leaves the body and the location of the defect. Also, magnitude of the reflected pulse is a measure of the size of the defect as viewed in the direction of travel of the sound waves.
Such ultrasonic test equipment is calibrated by using holes, v-notches, or half-circle profiles which are drilled or otherwise machined in test blocks or the material being tested. One such machining technique is that of a electric discharge machine the operation of which involves considerable time and expense. These profiles are drilled or machined to different depths to form surfaces which reflect sound waves entering the test block or material being tested. For a test standard the inspector usually works with profiles of one size and different depths. The ultrasonic test equipment is calibrated by transmitting sound pulses into each of these profiles. This way the data obtained from the calibrated blocks can be used to determine the size of flaws and the depth of flaws within the material being tested by the equipment. The profiles of different sizes and depths can also be placed in the material being tested to obtain similar information.
Considerable difficulty has been experienced in the past with drilling or machining of the profiles so as to provide a surface at the bottom and edge of each which is not only parallel or at the right angle to the surface of the block from which the ultrasonic sound beam is transmitted into the block, but also is truly flat so as to provide a reflecting surface of the desired area facing the path of travel of the sound beam. Also, with the prior art profile forming techniques, it is difficult to obtain the same surface finish at the bottom or edge of each profile in order that these surfaces have essentially the same reflective characteristics to sound beams.
In view of the above enumerated difficulties of forming an impression in a material which can be used as a reference standard, it is an object of this invention to provide a method of forming an impression profile in the material which does not require drilling.
It is yet another object of this invention to provide a method for forming an impression profile in a material which can be used as a reference standard which does not require other expensive and time consuming machining processes such as the use of an electric discharge machine.
Yet another object of this invention is to provide a method for forming an impression profile in a material standard by the use of a die stamp.
Still another object of this invention is to provide a method for forming an impression profile in a material standard wherein the profile takes the shape of the letter I.
Another object of the invention is to provide a method for forming an impression profile in a material standard wherein the impression has consistent repeatability when impressed in various materials used for standards.
A further object of the invention is to provide a method for various classes of inspection by varying the dimensions of the die stamp, and thereby the sizes of the impressions made in the material standard.
Another object of the invention is to provide a method for forming an impression profile in a material standard with the use of hand tools.